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Background

Pain is likely the most prominent symptom affecting cancer patients' quality of life

A majority of patients will have not only a baseline amount of pain, but also "breakthrough pain", referring generally to a transitory exacerbation of pain that occurs periodically over and above the baseline pain

A baseline amount of medication, often opioid, is usually prescribed to combat the baseline amount of pain the patient experiences

Supplemental opioid medications are often prescribed to manage breakthrough pain

However, breakthrough pain had not been empirically assessed prior to the publication of this article

This reports on the factors influencing breakthrough pain and the characteristics of breakthrough pain in a population of cancer patients

Materials and Methods

Ninety patients were initially evaluated

All patients were required to have baseline pain that was mild or moderate (those with severe baseline pain were said to have uncontrolled pain and were excluded)

Although baseline opioid use was not a requirement, whatever amount of medication (or no medication) the patient was on for baseline pain was required to be a stable dose for 2 or more days. Seventy patients achieved this initial criteria

Forty-one of these patients reported at least one episode of breakthrough pain that was the required grade of 'severe' or 'excruciating'. These patients reported 51 different pain syndromes which formed the data set for the study

Questionnaires were filled out by the patients for the assessment of their breakthrough pain:

Temporal characteristics, including frequency, type of onset (time to progress from first perception to maximal intensity), and duration were assessed

Pain severity was assessed using a five-category scale of 'none', 'mild', 'moderate', 'severe', or 'excruciating'. Again, all sessions of breakthrough pain were required to be either 'severe' or 'excruciating'

Location of the pain was also assessed, basically to determine if the location differed from that of the baseline pain

Each episode was characterized as spontaneous or as being precipitated by an event, such as movement, cough, etc.

Pain was characterized as somatic (musculoskeletal), visceral (involving a hollow viscus), or neuropathic (burning or lancinating in a nerve's distribution)

Pain was described by etiology and related to either the tumor itself, treatment, or neither

Patients were asked to describe the factors they believed to be responsible for the cessation of the pain

Results

The median number of episodes of breakthrough pain was four, though five patients had more than 10 episodes of breakthrough pain during the prior day

43% of patients reported an onset to maximal intensity within 3 minutes, with a median duration of pain of 30 minutes. 41% of patients had pain characterized by both rapid onset (less than 3 minutes) and rapid dissipation (less than 20 minutes)

96% of the episodes of breakthrough pain occurred in the same location as the baseline pain. Most cases of breakthrough pain therefore represented a transient exacerbation of the baseline pain already being experienced

Onset of breakthrough pain occurred in 29% of the patients at the end of the dosing interval of the regularly scheduled analgesic for baseline pain

55% of the episodes of breakthrough pain had a precipitating factor, including most commonly, movement, walking, coughing, and bowel distension

33% were somatic, 20% were visceral, 27% were neuropathic, and 10% were mixed

76% of the episodes were specifically related to the known tumor(s) and 20% were attributed to treatment

Most patients could identify the intervention that stopped the pain. These included most commonly the use of a rescue dose of medication, change in position or movement, or a combination of these

Author's Conclusions

There are obvious biases and limitations to the study, though it serves as a good first step to identify the characteristics of breakthrough pain

Transient pains were extremely common in this population of cancer patients with a great variety of precipitating events

These pains are diverse in presentation

Additional surveys are needed to characterize these pains, their etiologies, their pathogeneses, and the efficacy of treatments

Scientific Implications

As stated, pain is an extremely prevalent symptom in cancer patients and episodes of breakthrough pain are very common. This study hoped to report on the characteristics of these episodes, for which it was successful. There were obvious limitations. All patients were evaluated in the pain clinic and therefore likely had difficult to manage pain. Also, the clinician could easily introduce bias and the questionnaire method of data collection is less than optimal. However, much information can be gained form this report. The most applicable to the clinical physician is the quick onset and quick dissipation of pain. This indicates that the rescue treatment of these episodes needs to be extremely quick in onset to be efficacious. Also, a fair number of episodes were neuropathic in nature, indicating that anti-convulsants or anti-depressants may be better suited to treat patients with this specific pain syndrome. The fact that 96% of the episodes were related to either the tumor itself or from the treatment of the disease indicates that physicians need to continually be aware of the possibility of breakthrough pain episodes and that these episodes need to be managed aggressively, so that the cancer patient's quality of life is optimized.